Px Suspension and Component Facts Flashcards
Undesirable effects pistoning creates
1) Generation of shear stresses on skin
2) Functional elongation of the px during swing phase
Most effective suspensions to reduce pistoning:
1) Atmospheric Pressure Suspension
2) Anatomic Suspension
3) Strap Suspension
4) Hinge Suspension
Preferred suspension whenever feasible
Atmospheric Pressure Suspension
Affects from non total contact with atmospheric pressure suspension:
1) Skin damage
2) Capillary breakages
3) Fluid Drainage
4) Thickening and furrowing of skin
5) Malignancy
3 Practical limitations from a suction socket:
1) Inability to don or doff the socket consistently
2) Inability to maintain vacuum
3) Inability of the skin to tolerate direct contact with the hard socket walls
Developer of the roll-on liner
Ossur Kristinsson of Iceland
ICEROSS stands for
Icelandic Roll-On Suction Socket
To create an effective vacuum seal how much of rubber must seal against the socket and extend onto the thigh?
2 cm
Next best suspension after atmospheric suspension:
Anatomic- advantage of anatomic contours
Where is a supracondylar wedge placed?
Area above the medial femoral condyle, just proximal to the adductor muscle
Besides suspension, what does the supracondylar wedge add?
Mediolateral control
Downfall of strap suspension:
1) Allow significantly pistoning
2) Less comfortable than atmospheric/anatomic suspensions
Suprapatellar cuff also known as:
Patellar Tendon Bearing (PTB) Strap
Suprapatellar cuff function:
Fit snugly against the suprapatellar tendon during swing phase, suspending the prosthesis over the proximal edge of the patella, and to gradually relax when the knee is flexed beyond 60 degrees so that sitting is comfortable
Primary indications today for the use of “joints and lacer” suspension:
Partially unload a fragile residual limb
Single-axis Ankle Foot-
increases knee stability
Solid Ankle-Cushion Heel Foot-
Popular world wide and has proven to be a very versatile, albeit basic, foot design, and very smooth motion clinically
Multi-axial Ankle Foot-
Suites uneven surfaces and absorbs some of the impact of walking
Flexible Keel Foot-
Pronation
Supination
Rollover
Makes walking easier
Advised for preparatory px, pediatric px’s, and not recommended aggressive explosive movements
Dynamic-Response Foot-
stores potential energy and releases it in the latter part of stance phase
Contraindication for dynamic response foot rx:
Amputee is unable or unwilling to load the forefoot, because the spring would be non functional
Single Axis Knee-
Pros:
Least expensive
Most maintenance-free
Con:
Has no inherent stability
Rx:
Pediatric application more common
Stance Control Knee
Pros:
Most commonly prescribed px knee in the world
Weight activated friction brake
Assists new amputees to learn to walk on a px safely
Appropriate for limited ambulators at a slow pace
Bilateral amputee application is for only one limb
Polycentric Knee
Pros:
Stability
Additional toe clearance at swing phase
Help produce a more biomechanically normal gait pattern
Manual Lock Knee
Pros:
Provide maximum knee stability
May permit feeble elderly patients to walk more rapidly
Cons:
Functionally too long
Creates abnormal gait deviation
Increases the energy cost of ambulation
Recommendation:
Toddlers and small children for stability
Hybrid Knees-
Most popular:
Polycentric combined with hydraulic/pneumatic unit to provide variable cadence swing-phase control
Microprocessor Control-
Pros:
Increases gait kinematic control
Increase energy efficiency in gait
Torque Absorber
Permits controlled transverse rotation
Absorbs the stresses of the amputees skin
Positional Rotator
Allows amputee to passively rotate the lower leg
Use when sufficient space between the knee and socket
Shock Absorbing Pylon
Increased comfort when descending stairs, stepping down curves, or getting out of a car
Main use for componentry
Match the biomechanical peformance of the components to the individual amputee’s functional goals and physical abilities.
